Interest in making well-defined linear polymers substituted with polar and/or functional groups has been spurred, in part, by the commercial utility of ethylene-vinyl alcohol (EVOH) copolymers. EVOH copolymers, as a class, exhibit excellent barrier properties toward gases and hydrocarbons and have found use in the food packaging, biomedical, and pharmaceutical industries. See Lagaron et al. (2001) Polym. Testing 20:569-577, and Ramakrishnan (1991) Macromolecules 24:3753-3759. Furthermore, the lack of understanding of the property-structure relationships in these materials has fueled academic interest in the microstructure of EVOH copolymers. See Ramakrishnan (1991), supra; Ramakrishnan (1990) Macromolecules 23:4519-4524; Valenti et al. (1998) Macromolecules 31:2764-2773; and Bruzaud et al. (2000) Macromol. Chem. Phys. 201:1758-1764. The most widely employed synthetic route to EVOH copolymers is the free radical polymerization of ethylene and vinyl acetate, followed by saponification (Ramakrishnan (1990)). These EVOH copolymers contain a degree of branching, much like low-density polyethylene (LDPE), and have a random distribution of alcohol functionality along the polymer backbone ((Ramakrishnan (1991); Valenti et al., supra), both of which limit the elucidation of the structure-property relationships in these materials.
The direct incorporation of polar functional groups along the backbone of linear polymers made via ring-opening metathesis polymerization (“ROMP”) is now possible due to the development of functional group-tolerant late transition metal olefin metathesis catalysts. Recently, Hillmyer et al. reported the ROMP of alcohol-, ketone-, halogen-, and acetate-substituted cyclooctenes with a ruthenium olefin metathesis catalyst (Hillmyer et al. (1995) Macromolecules 28: 6311-6316). However, the asymmetry of the substituted cyclooctene allowed for head-to-head (HH), head-to-tail (HT), and tail-to-tail (TT) coupling, yielding polymer with regiorandom placement of the functional groups. A similar problem was encountered by Chung et al., who reported the ROMP of a borane-substituted cyclooctene with an early transition metal catalyst followed by oxidation to yield an alcohol functionalized linear polymer (Ramakrishnan et al. (1990), supra). A solution to this regiorandom distribution of functional groups was reported by Valenti et al., who used the acyclic diene metathesis (ADMET) polymerization of an alcohol-containing symmetric diene (Valenti et al., supra; Schellekens et al. (2000) J. Mol. Sci. Rev. Macromol. Chem. Phys. C40:167-192)) However, the molecular weights of these polymers were restricted to <3×104 g/mol by ADMET, and their rich hydrocarbon content limits the barrier properties of the final EVOH copolymers (Lagaron et al., supra).
Transition metal carbene complexes, particularly ruthenium and osmium carbene complexes, have been described as metathesis catalysts in U.S. Pat. Nos. 5,312,940, 5,342,909, 5,831,108, 5,969,170, 6,111,121, and 6,211,391 to Grubbs et al., assigned to the California Institute of Technology. The ruthenium and osmium carbene complexes disclosed in these patents all possess metal centers that are formally in the +2 oxidation state, have an electron count of 16, and are penta-coordinated. Such complexes have been disclosed as useful in catalyzing a variety of olefin metathesis reactions, including ROMP, ring closing metathesis (“RCM”), acyclic diene metathesis polymerization (“ADMET”), ring-opening metathesis (“ROM”), and cross-metathesis (“CM” or “XMET”) reactions. Examples of such catalysts are (PCy3)2(Cl)2Ru═CHPh (1) and (IMesH2)(PCy3)(Cl)2Ru═CHPh (2): In the above molecular structures, “Mes” represents mesityl(2,4,6-trimethylphenyl), “Ph” is phenyl, and “Cy” is cyclohexyl.
Catalysts (1) and (2) have been shown to afford the ROMP of many substituted cyclic olefins. See, for example, Bielawski et al. (2000) Angew. Chem., Int. Ed. 39:2903-2906; Sanford et al. (2001) J. Am. Chem. Soc. 123:6543-6554; Amir-Ebrahimi et al. (2000) Macromolecules 33:717-724; and Hamilton et al. (2000) J. Organomet. Chem 606:8-12. Recent development of ruthenium catalysts, such as (2), coordinated with an N-heterocyclic carbene has allowed for the ROMP of low-strain cyclopentene and substituted cyclopentene. Bielawski et al., supra. The ROMP of a symmetric cyclopentene yields a regioregular polyalkene, as no difference exists between HH, HT, and TT couplings. Hence, the ROMP of alcohol- or acetate-disubstituted cyclopentene monomers was attempted (Scheme 1). 
Unfortunately, neither catalyst (1) nor the more active (2) could afford the ROMP of these cyclopentene monomers.
Accordingly, there is a need in the art for a method of synthesizing polymers using catalysts that are tolerant of functional groups and a process that enables precise control over molecular weight, molecular weight distribution, and polydispersity. Ideally, such a method would also be useful in the synthesis of regioregular and/or telechelic polymers. The invention is directed to such a method, and now provides a highly effective polymerization process in which a ROMP reaction is carried out using substituted bridged bicyclic or polycyclic olefin monomers and a transition metal carbene complex such as (1) or (2). The process can be used to synthesize regioregular and/or telechelic polymers, in a manner that enables careful control over polymer properties such as molecular weight and polydispersity.